Electrooptical transmission system



' June 30, 1931. F, GRAY 1,812,402

ELECTROOPTICAL TRANSMISSION SYSTEM Filed Sept. 30, 1929 ATTORNEYPatented June 30, 1931 UNITED STATES PATENT OFFICE FRANK GRAY, OF NEWYORK, 1v. Y., ASSIGNOR TO BELL TELEPHONE LABORATORIES, INCORPORATED; onNEW YORK, N. Y., A CORPORATION on NEW YORK ELECTROOPTICAL TRANSMISSIONSYSTEM Application filed September 30, 1929; Serial No. 396,093.

I er izing one or more moving lamps such as may be employed forproducing an image under control of an image current.

In accordance with another feature of the invention there are provided aresonant circuit which is supplied with current from an alternatingcurrent source, and a source of signaling current, for example, an imagecurrent, for controlling the resonance characteristics of said circuitto vary the amplitude of the current flowing therein in accordancecomprises a spirallyarranged row of primary with the variations of thesignaling current.

In a Specific form of the invention hereinafter described in detail byway of example, an apparatus for producing television'images sourcesof'light such as electric lamps attached to a revolving disc near theperiphery thereof and adapted to cros's'the field of view in successionto build up an image. Each lamp is connected to a circuit including aWinding tone values of successively scanned'elemental' attached to thedisc through which the lamp is inductively energized, while passingacross the field of View, from a source of image current havingVariations corresponding to the areas of a field of View. The imagecurrent may be a-current of varying amplitude which is supplied directlyto the lamps through a inductive coupling. In a preferred embodiment,however, the circuit including each lamp is a tuned circuit having afixed resonance characteristic which is supplied with energy fromacurrent source, the frequency of which varies in accordance with thetone values of successively scanned elemental areas ofthe field of view.Instead of this arrangement tlie lamp circuit may be suppliedinductively with current from a source of constant frequency and theresonance characteristics of the lamp circuit may be varied inaccordance with the variations of the received'image current. In any ofthese arrangements one'or more lamps in fixed position may be employedin place of the moving lamp or lamps for producing an image of a fieldof view.

Illustrative en'lbodiments of specific forms of the invention are shownin the accompanying drawings.

F 1 of the drawings diagrammatically illustrates a televisiontransmitting and receiving system;

Fig. 2 illustrates a system for producing signals, which system may beemployed, for example, in place of a portion of the image producingsystem shown in Fig. 1; and

Fig. 3 illustrates a modification of the sy tem shown in Fig. 2.

Referring now to Fig. 1 of the drawings a held of view defined by anopening 16 in the screen 17 and including an object 10 is scanned by arapidly moving pencil of light rays from a source 12 such as an electricarc. Concentrating lenses 13 direct the rays of light from the source 12upon a limited area of a scanning disc 14. This disc is provided in thewell-known manner with a. series of spirally arranged apertures and isrotatably driven by a motor 15. Each slender pencil of rays passingthrough a single aperture in the scanning disc and through the opening16 of the screen 17 scans a iinea r element of the field of viewcomprising the object 10 at such a rate that every portion or elementalarea of the held of view is illuminated approximately 16 times persecond. The light of varying intensity reflected from the object- 10 isdirected upon the light sensitive surface of a photoelectric cell 20which is subjected to an electromotivc force of battery 11 and whichcomprises a central electrode or anode 21 and a light sensitiveelectrode or cathode 22. The variations in light are translated in awell-known manner. into variations of electrical current in the circuit23. This photoelectric current is amplified by the amplifying equipment24. The alternating current from the amplifier 2a is impressed throughtransformer 26 upon a line 27 connecting the transmitting and receivingstanected 'to rent received from the vacuum tube oscillator.

held of view to produce an image current is disclosed in greater detailin applicants copending application, Serial No. 227,649, tiled October21, 1927. V I

At the receiving station the image curline 27 is impressed through atransformer 28 upon the amplir'ier 29 with whichis associated a gaincontrol or regulating circuit ncluding a res stance element 32. Amovable contact 33 is selectively associated with the resistance element32 to impress a desired potential on the winding of an electromagnet34ffor mechanically vibrating astructure such as the armature 35. Apiezo-electriccrystal or other device may be employed in place of theelectromagnet 34. The armature 35 is rigidly cona movable plate 37 of anelectric condenser 38 which also hasa fixed plate 39. Thiscondenser'forms a capacitative'portion of an oscillatory circuit which.controls the frequency of the-current produced by a source ofalternating current 41, such as a The alternating current from thissource preferably has a frequency higherthan any frequency componentpresent in the received image cur rent so that the variationsin theinstantaneous values of amplitude of the alternating current will notinterfere with the production of an image. The frequency of the currentproduced by the oscillator 41' and impressed upon the primarytransformer Winding 42 varies in accordance with the capacity variationsof the condenser 38 and, therefore,in accordance with the amplitude ofthe incoming picture current.

The image field at the receiving station consists of the relativelysmall area 46 markedin dotted lines on the disc 47. This areamay bedefined by a screen or limited by the association between the secondarywinding 48 This field is illuminated so as to produce an image by meansof a series of small lamps 51 arrangedspirally upon the rotatable receiving disc 47 in a pattern similarto that of the spirally arrangedapertures in the scanning,

disc 14 at the transmitting station. The lamps may each be vieweddirectly or through a small aperture in a screen associated with eachlamp. These lamps may be arranged to construct. an imagelarger orsmaller in size than the opening 16 in the screen 17 at the transmittingstation.

Each of the lamps 51 is connected in a resonant circuit comprising oneof the inductive elements 48 and a capacitative element 52, the resonantfrequency of each of these circuits'preferably being such, with respectto the frequency of the current produced by the oscillator 41, that thecurrent through the lamp is at a low value when the amplitude of thereceived image current is and the primary winding 42.

zero or of a low value. As the amplitude of the received image currentactuating the device 34 increases, the frequency of the current producedby theoscilla'tor 41 will decrease and approach the resonant frequencyofthe circuits including the lamps 51. As a result, the amplitude of thecurrent actuating the lamp connected to the winding 48 which is adjacentto the winding .42 at this instant will be increased and thelamp .willemit light of correspondingly higher intensity. The amplitude of thecurrent flowing in the successively energized lamp circuits andtherefore the intensity of the light emitted by the successive lampswillvary in accordance with the frequency variations of the current from thesource 41 and, therefore, in

accordance with the amplitude v riations of the received image currentor the tone values of the successive elemental'areas of the field ofview which is scanned at thetransmitting and the disc 47 at thereceiving station are maintained in synchronism and in phase by the useof any suitable synchronizing arrangement such as disclosed, forexample, in the patent to H. M. Stoll-er and E. R'Morton, No. 1,763,909,June 17, 1930. If desired, these discs may be maintained in synchronismand in phase by means of independent sources of constant frequencyenergy at each station such as disclosed, for example, ina copendi'ngapplication of A. Marrison and J. W; Horton, Serial No. 256,784, filedFebruary 24, 1928.

In the modified arrangement shown in Fig. 2 the received image currentis impressed on a line which is connected to an electromagnet 61. Thiselectromagnet controls the capacity of a condenser 63 in a mannersimilar to that in which the capacity of condenser 38 of Fig. 1. iscontrolled. The condenser 63 forms a part of a-resonant circuit whichincludes a lamp 64 and a transformer winding 65. This circuit isenergized through the winding 66 by energy from the source 67 ofalternating current having a constant. frequency. As the capacity'of thecondenser 63 is changed in accordance with the amplitude variationsof'the image current impressed on the electromagnet 61 the naturalresonance of the circuit including the lamp 64 and the amplitude of thecurrent from source 67 flowing in the resonant circuit is changedcorrespondingly. The intensity of the light emitted by the lamp 64therefore varies in 'accordance with the amplitude variations of theimage current flowing in the line 60.

In the embodiment of the invention shown in Fig. 3 a source of imagecurrent is connected to the input circuit 7 0 ofthe electric dischargeamplifier 71' the output circuit of which is connected to a transformerwinding 72. A lamp 7 6'connected in a resonant circuit includingacapacitative element 77 and an inductive winding 74: is energizedthrough transformer winding 7 3 by current from the source of constantfrequency alternating current 72. As the image currentpotentialimpressed on the input circuit of the electric dischargeamplifier 71 varies in: amplitude the output or anode-cathode impedanceof the electric discharge amplifier is: changed correspondingly and thusthe effective impedance of the winding 74 which is associated: with thewinding 72' is changed correspondingly. As the effective impedance ofthe winding 74 changes the frequency at which the circuit including thelamp 76 is resonant changes, thus causing a correspond ing change in.the amplitude of the current from source-72 flowing in. this circuit.

It is obvious that when employing either of the arrangements shown inFigs. 2 or 3, a plurality of resonant circuits including the transformerwinding, the condenser and the lamp could be. provided and mounted on arotatable disc asshown in Fig. 1. In. such an arrangement theelectromagnet 61 and the winding 66,: of Fig. 2' or the winding 72 and73 of Fig. 3"wouldf be em loyed in place of the winding 42; shown in 1.In the former case condensers 63- of the moving circuits: are located sothat their paths are adjacent the stationary magnet 61 and the windings65 of the moving circuits are so located that theirpath: of travel isadjacent stationary coil 66.. Thestationary elements are of differentlength than the moving elements as indicated in Fig.1- This is true alsowhen the arrangement shown in Fig. 3 is sub stituted for the specificarrangement shown inFig. 1..

In any of the arrangements heretofore described, a singlefixed lamp andits associated circuit may be. employed, instead of a plurality ofmovable lamps, together with an apertured scanning; disc such as thed1sc 14.- shown in Fig. 1. Itis also obvious that a bank of lamps may beemployed for reproducingthe image, each lamp being connected to a sourceof energizing current from a rotating commutator. Image producing systems somewhat similar to both of these arrangements are disclosed inapplicants copending application to which reference has been. madehereinbefore.

While an arrangement maybe employed in. which the lamp circuits shown inFig. L, for example, are non-resonant and in which the received imagecurrent of varying amplitude is impresed directly on the winding 42,.thearrangement shown in 1 would be preferablei'n many-cases because it) hasthe advantage that the relatively small amplltude variations ofthereceived image current are employed to produce relatively largevariationsinthe current from a local source wh ch energizes each lamp.An image of correspondingly increased brillancy is thus produced.

What is claimed? is:

1. In combination, a source of continuously varying signaling current, aresonant circuit, light control means in said circuit, a source ofalternating current for supplying current to said resonant circuit, andmeans responsive to said signaling current for controlling the resonancecharacteristics of said circuit to vary the amplitude of the currentflowing therein in accordance with the variations of said signalingcurrent.

2. An electro-optical' image producing system comprising a source ofimage current, two inductively coupled circuits at least one of which isresonant, a lamp in one of said: circuits, and means for changing theresonance characteristics of said one circuit in. accordance with acharacteristic of said image current.

3. In combination, a source of varying frequency current ofsubstantially constant amplitude, a plurality of resonant circuits, andmeans for inductively impressing current from said source upon saidresonant circuits in succession to cause the current flowing to have anamplitude which corresponds to the frequency of the current from saidsource.

4. In a signaling system, a transmitting station and a receivingstation, a source of current at said: transmitting station, means forvarying the amplitude of said current in accordance with a signal to betransmitted, means for transmitting said varying amplitude signalingcurrent to said receiving sta; tion, a source of current of highfrequency with respect to the frequency components of said signalingcurrent at said receiving station, a resonant circuit associated withsaid source of high frequency current, and means for varying therelation between the frequency of the currentfrom said source and thefrequency at which said circuit is resonant in accordance with. theamplitude variations of said signaling current to cause the amplitudeofthe current in said resonant circuit tovary correspondingly.

5. In an electro-opt-ical system, a plurality of stations, a source ofvarying amplitude signaling current at one of said stations, means fortransmitting signaling current from said source to said other station, asource of high frequency alternating current at said other station, aresonant circuit in--,

cluding a'source of li ht to be energized by current from said source,and means for varying the relation between the frequency of the currentfrom said high frequency source, and the frequency at which said circuitis resonant in accordance with the amplitude variations of said receivedsignaling current for correspondingly varying the SOQ III]

amount of light emitted from said source of light. i

6. A television system'compri'sing means including a source oftelevision image current, a member mounted for rotation, a number oflamps and circuits therefor mounted on said rotary member, said lampsbeing arranged to bemoved across a field of view by the rotation of saidmember, and current supply means to inductively energize each lamp byenergy-which varies in accordance with the variations of said imagecurrent While said lamp is'in' the field of View.

7 7. A television system comprising means at a transmitting station forproducing an image current which varies im ampltiude in accordance withthe tone values of successively scanned elemental areas of a field ofview, an imageof which is to be produced, means at. a receiving stationfor presenting to view in rapid succession successive elemental areas ofan image field in correspondence with the scanning of the field of viewat said transmitting station, a source of high fre-' quency alternating.current and a resonant circuit at said receiving station, and meansforvarying the relation between the frequency of the current from said highfrequency source and the frequency at which said circuit is resonant inaccordance with the amplitude variations of said image current forcontrolling the illumination of successive ele-V mental areas of'saidimage field.

8. ,A television system comprising means at a transmitting station forscanning the elemental areas of a field of view in succession to producean image current, a source of high frequency current at a receivingstation,

meansrfor controlling the frequency of the current from said source inaccordance with the amplitude varlations of sa1d lmage current,arotatable disc drlven 1n synchronism and in phase with said scanningmeans, a

plurality of similar spirally arranged lamps mounted on said disc, aplurality of resonant circuits of similar characteristics, oneassociated-with, each of said lamps, and means for inductivelyenergizing said lamps by current from said high frequency source forpro-' ducing an image of said field of view.

r 9. An ele'ctro-optical system comprising an if electric dischargedevice having an input and an output circuit, a source of energizingcurrent connected to the input circuit of said device for controllingthe output impedance thereof, a resonant circuit including acapacitative element, an inductive element and a lamp, a; secondinductive element connected in the output circuit of said electric dischggge device for controlling the effective impedance of the inductiveelement in said resonant circuit in accordance with the variations ofthe output impedance of said electric discharge device, and a source ofconstant image.

frequency current'for supplying energy to.

current, a rotatable member, a plurality of,

circuits mounted on said rotatable member, a light controlling means ineach of said circuits, stationary means adjacent said rotatable memberbut out of contactctherewith energized by said modulated current forimpressing modulated current upon said circuits in succession whilecrossing a field of view, and means for continuously rotatingsaidrotatable member.

11. Television apparatus comprising a large number of energy translatingelements to be successively energized during the production of an imageand distributing means for television image current associated therewithcomprising a rotatable member, a plurality of inductive elements carriedby said member, and stationary inductivemeans adjacent the paths oftravel of said moving inductive elements and cooperating therewith inturn to effect the transfer of saidtelevision'current between saidstationary an said moving inductive means. 7

12. Television apparatus comprising a large number of energy translatingmeans to be successively energized during the production of an imagemade up of line series of elemental areas and distributing means forhigh frequency television image current associated therewith comprisinga rotatable member, a plurality of inductive elements carried by saidmember and having the same path of travel, and stationary inductivemeans adjacent said path and cooperating with said moving inductiveelements in turn to effect the transfer of said television currentstherebetween, said stationary inductive elements extending in saiddirection of travel a distance at least equal to the total length ofsaid path of travel divided by the number of line series of elementsused to form the 13. In an electro-op-tical image producing system,apparatus at a receiving station comprising a circuit, light-controllingmeans associated with said circuit and supplied with current therefrom,means for supplying alternating current to said circuit, means forvarying, in accordance with the received image current, the amplitude ofsaid alternating current supplied to said light controlling meanscomprising means for varying the ratio of the natural frequency of saidcircuit to the frequency of current therein.

14. An electroc-optical image producing system comprising a resonantcircuit, a source of alternating current in said circuit, lightcontrolling means in' series with said source in said circuit, and meansfor varying the relative values of the frequency of current from saidsource and the frequency at which said circuit is resonant forcorrespondingly yarying the amplitude of the current there- 1n.

15. In an electro-optical image producing system, a plurality ofcircuits, light controlling means associated with said circuitsrespectively and supplied with current therefrom, means for supplyingalternating current to said circuits in succession and means for varyingthe amplitude of said alternating current in accordance with the tonevalues of an object an image of which is to be produced comprising meansfor varying the ratio of the natural frequency of said circuits to thefrequency of current supplied thereto. 16. In an electro-optical imageproducing system, a plurality of circuits, light controlling meansassociated with said circuits respectively and supplied with currenttherefrom, means for supplying alternating current to said circuits insuccession comprising a rotatable element upon which said circuits andlight controlling means are mounted, and means for varying the amplitudeof the alternating currents supplied to said light controlling means inaccordance with the tone values of an object an image of which is to beproduced comprising means for varying the ratio of the natural frequencyof said circuits to the frequency of current sup plied thereto.

In Witness whereof, I hereunto subscribe my name this 28th day ofSeptember, 1929. FRANK GRAY.

